Fabrication of a high-aspect-ratio structure (HARS) and a 3D feed-horn-shaped structure array for a 3D MEMS antenna array by using a novel UV lithography apparatus

Abstract

This paper reports a, novel UV lithography technique for fabricating a 3-dimensional (3D) feed-horn-shaped structure mold array, and obtaining parallel light by using a mirror-reflected parallel-beam illuminator (MRPBI) system. A 3D feed-horn-shaped micro-electro-mechanical systems (MEMS) antenna has some attractive features for array applications, which call be used to improve microbolometer performance and to enhance the optical efficency for thin film transistor-liquid crystal display (TFT-LCD) and other display devices. Since MEMS technology has faced many difficulties in the fabrication of a 3D feed-horn-shaped MEMS antenna array itself, The purpose of this paper is to propose a new fabrication method to realize a 3D feed-horn-shaped MEMS antenna array by using a mirror-reflected parallel-beam illuminator (MRPBI) System with an very slowly rotated, inclined x-y-z stage [1-5]. With a conventional UV lithography apparatus, it is very difficult to fabricate high-aspect-ratio structures (HARS) because a typical UV lithography apparatus cannot produce perfectly parallel light. From a theorectical anlysis, a columnar illuminator over 6 in in height is required to achieve parallel light, but generally a laboratory height is not 6 m. An essential idea of this research is to make a light ray with long propagation by using a reflective mirror and a conventional UV-lithography apparatus for creating parallel light in a small lab space. Also, a novel method of lithography was tried to make a 3D structure array by exposing a planar wafer to the generated parallel light and rotating an inclined x-y-z stage at, an ultra-slow rate. An optimization of the 3D structure array can be achieved by simulating a 3D feed-horn MEMS antenna. By using a high-frequency structure simulator (HFSS), a vertical sidewall array and 30degrees tilted sidewall array, we achieved a 300-mum-high structure array using a MRPBI system, which was confirmed using scanning electron microscopy. A high-aspect-ratio, 300-mum, thick sturucture with 30degrees tilted sidewalls was fabricated using a SU-8 negative photoresist, and a 100-mum vertical sidewall structure array was fabricated using a PMER negative photoresist. The feasibility of fabricating both a 3D feed horn MEMS antenna, and a mold array was demonstrated. In order to study the effect of this new technique, we simulated the 3D feed-horn-shaped MEMS antenna array had been simulated with high frequency structure simulator (HFSS) and then compared the results with those from traditional 3D theoretical antenna models. As a, result, it seems possible to use a 3D feed-horn-shaped MEMS antenna in the tera-hertz range to improve microbolometer performance and to fabricate several optical MEMS devices.